The present invention relates to ignition systems for use with spark-ignited internal combustion engines. More particularly, the present invention relates to improvements in the construction of a stator apparatus for use with such an ignition system.
Ignition systems for small gasoline engines include a transformer having a primary coil and a secondary coil related by a predetermined step-up ratio. The transformer coils are wound about a magnetically permeable core which is fixedly mounted with respect to the engine. A magnet assembly is provided, typically on the engine flywheel, to revolve about an axis in synchronism with operation of the engine. During operation, pole faces of the magnet are periodically moved past opposing pole faces of the core as a result of the magnet's revolution. In this manner, a time-varying magnetic flux is generated in the core.
These ignition systems have generally been divided into two broad classes, i.e., inductive type and capacitive discharge ("CD") type. Ignitions of each class include various circuit components connected to the primary coil of the transformer. Such circuit components utilize the time-varying flux produced in the core to cause a change in current flowing through the primary coil. As a result, a desired higher voltage will be induced on the secondary coil, which is connected to the engine's spark plug.
The transformer coils and various other circuits components are typically maintained within a coil housing mounted on one or more legs of the core. The overall stator apparatus comprising the core, along with the housing and circuitry contained therein, is typically attached to the cylinder head of the engine. Specifically, bolts extending through the core engage threaded bosses on the engine head to maintain the stator apparatus in position.
The electrical circuitry of the stator apparatus is electrically connected to the cylinder head to maintain a relative ground for the various voltage levels produced therein. Generally, this ground is established by a grounding member extending from the top of the stator housing and maintained in contact with the core. Various configurations have been provided for this grounding member. For example, electrical connection between the core and the grounding member has often been established by spot welding the grounding member to the core. While effective in providing the desired electrical connection, this technique has added a welding step to the process of assembling the stator unit. Other configurations have also been provided in which contact between the grounding member and the core is maintained frictionally. As will be explained in more detail below, these prior art frictional grounds may not be optimal in many applications.